Time-domain eyewidth measurement of an optical data link operating at 200 Mb/s

For optical data links a time-domain eyewidth can be defined and measured. The eyewidth is a useful parameter for data communication system designers. The method used to measure eyewidth involves a bit error rate test set (BERTS) and a variable delay generator. The delay generator is used to vary the phase between the reference data and the data returned from the device under test (DUT). A time-domain error spectrum can be measured by counting the bit errors at each phase. From this spectrum the eyewidth can be determined at any bit error rate (BER). In this paper, an automated method for making eyewidth measurements is presented, along with results for optical receivers and optical transmitters. Also discussed are jitter measurements for recovered clock signals. The measurement method is also compared with more traditional jitter measurement methods.